Spark plug protectors



Sept. 13, 1955 J. P. ARVANlTAKlS SPARK PLUG PROTECTORS Filed NOV. 27, 1950 INVENTOR rJH/VEA 12 VA N/TA K/s,

ATTORNEYS United States Patent 0 SPARK PLUG PROTECTORS John P. Arvanitakis, East Gary, Ind.

Application November 27, 1950, Serial No. 197,810

4 Claims. (Cl. 123-169) This invention relates to spark plug protectors for preventing an accumulation of moisture upon the surface of the insulator member.

The invention comprises generally a housing, hood or jacket surrounding the insulator and snugly embracing the same and providing a multiplicity of dead air spaces between the surface of the insulator and the surrounding atmosphere.

The primary object of the invention is to prevent contact of atmospheric air with the insulator to obviate condensation of moisture contained in the air upon the surface of the insulator.

An additional object of the invention is to retard the interchange of heat between the insulator and the surrounding atmosphere.

Another object of the invention is to permit the protector to accommodate itself to insulators of various sizes and surface contours.

It is also an object of the invention to absorb any moisture which may have accumulated upon the insulator prior to installation of the protector.

A further object of the invention is to protect the insulator from grease, dirt or liquids, particularly such as may be precipitated upon it by action of moving parts of the engine in connection with which the spark plug is employed.

The invention resides in the specific construction, arrangement and combination of parts as will appear from the embodiments thereof described in the following specification and illustrated in the accompanying drawing, wherein:

Figure l is a side elevation of a conventional spark plug showing the invention in vertical cross section as applied thereto.

Figure 2 is a plan view of one of the discs shown in section in Figure 1.

Figure 3 is a view similar to Figure 1 showing a modified form of the invention.

Figure 4 is a detail view showing a bushing for insulating the central electrode of the spark plug from the casing of the protector when formed of metal.

Referring now more particularly to the drawings, the numeral 1 designates a conventional spark plug for internal combustion engines having the typical insulator member 2 usually formed of porcelain. The protector of this invention is designated generally in the drawing by the numeral 3 and comprises a tubular casing or hood 4 surrounding the insulator 2 and spaced therefrom by a removable heat insulating filler or cartridge of electrical insulating material generally indicated by the numeral 5. The inner or lower edge of the casing 4 is spaced from the metal body of the plug a distance greater than that across the spark gap thereof to prevent a short circuit at this point. The casing is preferably formed of an electrically insulating composition such as thermoplastic material, compressed fiber or hard rubber but may be formed of metal. When formed of metal the casing is insulated from the electrode 13 of the plug by a bushing 14 as shown in Figure 4. The filler 5 is supported within the casing 4 upon an inturned annular flange 6 at one end of the casing. The flange 6 is inclined upwardly to position the bottom of the filler away from the open end of the casing in order to protect it from moisture, grease and dirt. A cover 7 is provided at the opposite end of the casing, and is held in position upon the casing by engagement of a bead 8 upon the casing seated in a complementary depression provided in the downturned flange 9 of said cover.

Referring to the preferred form of the device shown in Figure 1, the filler 5 is formed of a plurality of superposed, centrally apertured alternately arranged layers 10 and 11 having their contacting faces cemented or otherwise bonded to form an integral structure independent of and readily removable from the casing 4, and disposed with the apertures therein arranged in longitudinal alignment defining a bore for the reception of the insulator. The apertures of the layers 10 are greater in diameter than the apertures of the layers 11. The apertures of the layers 11 are all of the same diameter but of a diameter not greater than the smallest cross sectional diameter of the portion of the insulator in contact with which said layers are adapted to be disposed in order that the device may fit insulators of various sizes.

As illustrated the tubular casing 4 is cylindrical and the layers 10 and 11 are circular discs and the apertures of said discs are circular apertures. However, the casing 4 may be square, hexagonal or of other cross sectional shape which is also true of the discs 10 and 11. Furthermore, while the apertures in the discs 11 are illustrated as being circuiar to cooperate with an insulator of circular cross section, said apertures may be of any other shape to fit the cross section of the insulator of the particular spark plug in connection with which the device is used.

The layers It and 11 are formed of flexible, heat insulating material preferably molded, compressed, matted or felted vegetable, animal or other fibers having electrical insulating properties such as paper, asbestos, wool, cotton or slag. Advantages are obtained when absorbent material is employed and also when the material of the fibers is of low specific heat. The material may be of a fireproof or heat resistant nature or may be treated in such manner as to impart such properties thereto.

The layers 11 as shown in Figure 2 are circular discs provided with circular apertures and are formed with radial slits 12 extending outwardly from the edges of said apertures whereby each disc readily accommodates itself to fit around an insulator at points of different diameters as shown in Figure 1 and also insulators of different diameters.

By reason of the alternate arrangement of the layers 10 and 11, the inner portions of the layers 11 are dis posed in spaced relation thereby forming dead air spaces around the insulator between the layers 11.

In the embodiment of the invention shown in Figure 3 the casing 4 is provided with a filler comprising a self sustained porous body of molded compressed, matted or felted fibrous electrical insulating material embracing the insulator 2 and intimately contacting its surface throughout a substantial part of the area thereof. The filler thus constituted provides a multiplicity of dead air spaces surrounding the insulator and functioning to prevent access of outside air to the surface thereof and to retain heat in the material of the insulator.

As is well known, the spark plug of an internal con1- bustion engine may fail to function properly by reason of the fact that the electrical current supplied thereto does not pass across the air gap between the terminals of the electrodes but follows a path of less resistance provided by an accumulation of moisture, grease or other matter upon the surface of the insulator of the plug.

Such an accumulation of moisture occurs with great frequency by reason of condensation from the surrounding atmosphere due to the insulator being of a temperature lower than the atmosphere. During operation of the engine heat is supplied to the material of the insulator so that no condensation takes place. The protector of the present invention when in place upon the plug acts to retain the heat of the insulator material and to shield the same from contact with the outside air, thus preventing condensation of moisture upon the surface of the insulator.

When the filler 5 is formed of material of low specific heat its temperature changes quickly in accordance with temperature changes in the surrounding atmosphere thus avoiding to a great extent such temperature differential as would tend to cause condensation of moisture.

Moisture absorbed from the air or other source by the material of the filler at the open end of the casing 4 is dispersed throughout the body of the filler 5 by capillary action and thus tends to prevent accumulation on the surface of the insulator. This is also true if the protector is installed upon a plug upon the insulator of which moisture has previously accumulated.

In the event, however, that the lower or inner end of the filler 5 becomes saturated or encrusted and establishes an electrically conductive path between the casing 4 and the insulator 2 such as would cause a short circuit, the filler may be reversed end for end or when constructed as shown in Figure 1 the lowermost layer 11 may be removed by cutting away flush with the adjacent layer 10.

The filler or cartridge 5 of Figure 1 may be used without the casing 4 and is effective to prevent condensation of moisture upon the insulator. However, the casing serves the purpose of protecting the filler or cartridge from damage by crushing or breaking in storage and and handling as well as from water, grease and dirt when in use.

Under operating conditions heat generated by the engine increases the temperature of the material of the tiller as Well as of the air in the spaces between the layers 11 in consequence of which all moisture is eliminated. When the heat thus supplied is dissipated the temperature of the insulator and the tiller become coordinated with that of the surrounding atmosphere. In the event of an increase in the temperature and moisture content of the atmosphere the tiller material being of low specific heat readily absorbs heat from the atmosphere and condensation by the filler material is thus avoided and the insulator being shielded from contact F with the atmosphere by the dead air spaces provided by the tiller, condensation upon the surface of the insulator is prevented.

Having thus described the invention, what i claim is:

1. A shield adapted for detachable application to the insulator of a spark plug comprising a plurality of superposed flexible layers of heat insulating material disposed one upon another in face to face contact, means for securing said layers in said superposed relation, each of said layers being provided with a centrally disposed aperture, the apertures of alternate layers having a diameter greater than the apertures of the intermediate layers, and

all of said layers positioned with the apertures thereof in longitudinal alignment to form a bore for the reception of the insulator of said spark plug.

2. A shield adapted for detachable application to the insulator of a spark plug comprising a plurality of superposed flexible layers of absorbent fibrous electrical and heat insulating material having their opposed faces disposed in contact and bonded to form a unitary structure, each of said layers being provided with an aperture, the apertures of alternate layers having a diameter greater than the apertures of the remaining layers, all of said layers arranged with the apertures thereof in longitudinal alignment to form a bore for the reception of the insulator of said spark plug.

3. A shield adapted for detachable application to the insulator of a spark plug comprising a tubular casing normally open at its opposite ends and provided with an inturned annular flange at one end and a removable cover at its opposite end, a heat insulating body member supported removably within said casing upon said flange and extending between the flange and said cover, said insulating body member formed of a plurality of layers of flexible heat insulating material arranged one upon arother in face to face contact, each layer having an aperture therein disposed in longitudinal alignment with the apertures of the other layers forming a bore for the reception of the insulator of said spark plug, the apertures of alternate layers being of greater diameter than the apertures of the intermediate layers.

4. In combination with the insulator of a sparl; plug, a tubular casing surrounding the same and supported thereon in spaced relation, an annular inturned flange at the inner end of said casing, a removable cover carried by the opposite end of said casing, a heat insulating body member removably supported within the casing upon said flange and extending between the flange and said cover, said insulating body member formed of a plurality of superposed centrally apertured flexible layers of heat insulating material disposed in face to face contact, the apertures of alternate layers being of greater diameter than the apertures of intermediate layers, said intermediate layers extending between the inner face of said easing into contact with the outer face of said insulator.

References Cited in the file of this patent UNITED STATE.) PATENTS 920,429 Burnham May 909 1,009,643 Bullock Nov. 22, 19H 1,245,931 Lanman Nov. 6, 1917 1,346,759 Meyer July l3, 1920 1,376,844 Weber May 3, 192i 1,794,673 Creager Mar. i93l 1,831,132 Nowosielski Nov. l0, l93l 1,988,859 Shumaker Jan. 22, 1935 2,008,573 Blount July to, 1935 2,269,076 Boll Jan. 6, 1942 2,553,114 Sailler May l5, 195i FOREIGN PATENTS 732,596 France June 20, 1932 

